Submerged arc welding system

Abstract

A submerged arc welding system includes a welding power supply, a welding wire feeder, a control unit for the welding power supply and the welding wire feeder, and a voltage sensor to detect voltage between the tip of the welding wire and a workpiece. Under the control of the control unit, the wire feeder feeds the welding wire at an initial feed speed at start of welding. Further, when the tip of the welding wire shorts to the workpiece, the wire feeder stops the feeding of the welding, and the welding power supply starts outputting welding current. Further, when a detection voltage detected by the voltage sensor reaches or exceeds a voltage threshold, the wire feeder starts feeding the welding wire at a welding feed speed for welding.

1 . A submerged arc welding system for performing submerged arc welding, the system comprising:
 a welding power supply including an inverter circuit and configured to supply electric power;   a wire feeder configured to feed a welding wire;   a control unit configured to control the welding power supply and the wire feeder; and   a voltage sensor configured to detect voltage applied between a tip of the welding wire and a workpiece,   wherein the control unit is configured to:
 cause the wire feeder to feed the welding wire at an initial feed speed at start of welding; 
 cause the wire feeder to stop the feeding of the welding while also causing the welding power supply to start outputting welding current, when a tip of the welding wire shorts to the workpiece; and 
 cause the wire feeder to start feeding the welding wire at a welding feed speed for welding, when a detection voltage detected by the voltage sensor reaches or exceeds a voltage threshold. 
   
     
     
         2 . The submerged arc welding system according to  claim 1 , wherein the welding power supply has output characteristics that match predetermined external characteristics, and
 a characteristic line representing the external characteristics has a slope that is equal to or greater than −40V/100A and equal to or less than −0.5V/100A.   
     
     
         3 . The submerged arc welding system according to  claim 1 , wherein the voltage threshold is equal to or greater than 20V and equal to or less than 40V. 
     
     
         4 . The submerged arc welding system according to  claim 1 , wherein the control unit causes the welding power supply to start outputting a short-circuit release current when the detection voltage is less than a predetermined voltage after a predetermined time has elapsed since the welding power supply starts outputting the welding current. 
     
     
         5 . The submerged arc welding system according to  claim 1 , wherein the welding wire includes a tip surface that is inclined with respect to a plane that is orthogonal to a direction in which the welding wire extends. 
     
     
         6 . The submerged arc welding system according to  claim 5 , further comprising a carriage that carries the wire feeder and that is configured to move along a welding line,
 wherein the control unit controls movement of the carriage independently from control of the wire feeder and the welding power supply at the start of welding.